Input: add common DT binding for touchscreens

Add common DT binding documentation for touchscreen devices and
implement input_parse_touchscreen_of_params, which parses the common
properties and configures the input device accordingly.

The method currently does not interpret the axis inversion properties,
since there is no matching flag in the generic linux input device.

Signed-off-by: Sebastian Reichel <sre@kernel.org>

3 files changed, 69 insertions, 0 deletions

diff --git a/Documentation/devicetree/bindings/input/touchscreen/touchscreen.txt b/Documentation/devicetree/bindings/input/touchscreen/touchscreen.txt
new file mode 100644
index 000000000000..d8e06163c54e
--- /dev/null
+++ b/Documentation/devicetree/bindings/input/touchscreen/touchscreen.txt
@@ -0,0 +1,27 @@
+General Touchscreen Properties:
+
+Optional properties for Touchscreens:
+ - touchscreen-size-x		: horizontal resolution of touchscreen
+				  (in pixels)
+ - touchscreen-size-y		: vertical resolution of touchscreen
+				  (in pixels)
+ - touchscreen-max-pressure	: maximum reported pressure (arbitrary range
+				  dependent on the controller)
+ - touchscreen-fuzz-x		: horizontal noise value of the absolute input
+				  device (in pixels)
+ - touchscreen-fuzz-y		: vertical noise value of the absolute input
+				  device (in pixels)
+ - touchscreen-fuzz-pressure	: pressure noise value of the absolute input
+				  device (arbitrary range dependent on the
+				  controller)
+ - touchscreen-inverted-x	: X axis is inverted (boolean)
+ - touchscreen-inverted-y	: Y axis is inverted (boolean)
+
+Deprecated properties for Touchscreens:
+ - x-size			: deprecated name for touchscreen-size-x
+ - y-size			: deprecated name for touchscreen-size-y
+ - moving-threshold		: deprecated name for a combination of
+				  touchscreen-fuzz-x and touchscreen-fuzz-y
+ - contact-threshold		: deprecated name for touchscreen-fuzz-pressure
+ - x-invert			: deprecated name for touchscreen-inverted-x
+ - y-invert			: deprecated name for touchscreen-inverted-y
diff --git a/drivers/input/input.c b/drivers/input/input.c
index 1c4c0db05550..97966d93e1f3 100644
--- a/drivers/input/input.c
+++ b/drivers/input/input.c
@@ -27,6 +27,7 @@
 #include <linux/device.h>
 #include <linux/mutex.h>
 #include <linux/rcupdate.h>
+#include <linux/of.h>
 #include "input-compat.h"
 
 MODULE_AUTHOR("Vojtech Pavlik <vojtech@suse.cz>");
@@ -2398,6 +2399,39 @@ void input_free_minor(unsigned int minor)
 }
 EXPORT_SYMBOL(input_free_minor);
 
+#if defined(CONFIG_OF)
+/**
+ * input_parse_touchscreen_of_params - parse common touchscreen DT properties
+ * @dev: device that should be parsed
+ *
+ * This function parses common DT properties for touchscreens and setups the
+ * input device accordingly. The function keeps previously setuped default
+ * values if no value is specified via DT.
+ */
+void input_parse_touchscreen_of_params(struct input_dev *dev)
+{
+	struct device_node *np = dev->dev.parent->of_node;
+	struct input_absinfo *absinfo;
+
+	input_alloc_absinfo(dev);
+	if (!dev->absinfo)
+		return;
+
+	absinfo = &dev->absinfo[ABS_X];
+	of_property_read_u32(np, "touchscreen-size-x", &absinfo->maximum);
+	of_property_read_u32(np, "touchscreen-fuzz-x", &absinfo->fuzz);
+
+	absinfo = &dev->absinfo[ABS_Y];
+	of_property_read_u32(np, "touchscreen-size-y", &absinfo->maximum);
+	of_property_read_u32(np, "touchscreen-fuzz-y", &absinfo->fuzz);
+
+	absinfo = &dev->absinfo[ABS_PRESSURE];
+	of_property_read_u32(np, "touchscreen-max-pressure", &absinfo->maximum);
+	of_property_read_u32(np, "touchscreen-fuzz-pressure", &absinfo->fuzz);
+}
+EXPORT_SYMBOL(input_parse_touchscreen_of_params);
+#endif
+
 static int __init input_init(void)
 {
 	int err;
diff --git a/include/linux/input.h b/include/linux/input.h
index 82ce323b9986..3dc3b1edc2af 100644
--- a/include/linux/input.h
+++ b/include/linux/input.h
@@ -531,4 +531,12 @@ int input_ff_erase(struct input_dev *dev, int effect_id, struct file *file);
 int input_ff_create_memless(struct input_dev *dev, void *data,
 		int (*play_effect)(struct input_dev *, void *, struct ff_effect *));
 
+#if defined(CONFIG_OF)
+void input_parse_touchscreen_of_params(struct input_dev *dev);
+#else
+static inline void input_parse_touchscreen_of_params(struct input_dev *dev) {
+	return;
+}
+#endif
+
 #endif